I have a question about cleaning out the EGR passage on my 2003 Monte Carlo, 2.4L, V6. Should compressed air blown into the EGR side of the passage result in compressed air coming out the hole in the bottom of the intake manifold?

As info, I removed the throttle body and cleaned the hole in the intake manifold that is behind the throttle plate (when assembled). It had a lot of carbon on it. I also cleaned out, as best I could, the horizontal hole in the manifold leading from the EGR valve towards the throttle body. But, I cannot get compressed air to blow either from the EGR side to the hole behind the throttle plate, or vice versa. This makes me wonder if there is an obstruction in the way which I can't see. I tried pushing a wire through, but can't get an open passage. The wire only goes so far and stops.

Another thing I did was crank the car without the EGR installed and test the exhaust gas from the tube that connects to the EGR valve, and the vacuum at the EGR manifold port. The exhaust gas flow was strong; but, there was no vacuum.

I'm thinking that the passage may turn up, down, or sideways after about three inches because that's as far as I can go with a wire from the EGR side of the passage. Thanks for any help you can provide.

You can use compressed air either way through the passage without any worry about damage, as it's just an aluminum tunnel. It does kind of turn before it gets to the actual EGR connection point so it is hard to get it all cleaned out. A small set of wire brushes helps greatly.

Let me ask you this, though. I assume you are trying to clean out the port because you either have a check engine light on due to a poor flow code or some other problem with the EGR system? I can tell you from much experience that cleaning the port out very rarely works well enough or long enough to fix the problem. I've been doing this for many years and have cleaned out hundreds of these for the same problem. Even after feeling it was perfectly cleaned out, the problem still arises at some point in the very near future. The only real way to correct this problem is to replace the upper intake plenum. Just some FYI for you to consider!

Yes, there must be a blockage if you can't get air through the passage. The actual passage, starting from the behind the throttle body where the 'hole' opening is on the bottom side of the plenum, you have to make a downward turn, then outwards a bit, then up, then out towards the EGR side of the port. It is very difficult to get anything to make those turns, but like I suggested earlier your best bet is some small, flexible wire brushes. That's what I use when I attempt to clean on of those out. You'll never get a coat hanger to make the route, and probably not a wire either. You may want to soak the passage with some penetrating oil and let it sit for a day or two and then try again (obviously leaving it apart and NOT driving it). Or, you could just do the inevitable and but a new plenum. That will solve the problem with a lot less headache.

Boy, it sure sounds like a snaking tunnel through from that hole. But, I will take your advice and see if I can find some real small wire brushes to use. Incidentally, I did soak the hole with Sea Foam overnight this weekend; but, it didn't loosen the carbon enough for 100psi to blow it out. Will try carb cleaner next time.

Well I finally got the passage cleaned out. I filled the hole behind the throttle plate with carb cleaner and let it soak about two hours. Then I used a coat hanger wire with two one inch bends to clean the hole, and another coat hanger wire with a four inch bend to clean from the EGR side. From the EGR side it took some screwing in hard on the wire to eventually open up the passage. It would only go in about four inches at first, but after this it went in about seven or eight inches. I then cleaned both ends with a 1/4" cylindrical wire brush, and blew both sides out with compressed air. This resolved the Check Engine light problem! Note: There is no way you can run a wire from one end of the passage to the other due to the limited access through the hole, and the turns when coming from EGR side.

[b]Update, 7/1/13[/b]Well it's been six months since I cleaned out the EGR passage, and the problem has not recurred. So, I'm pleased with the results. But, I would caution anyone reading this that you may have to do a lot of trial and error bending coat hanger wires to get the right bends to open up a clogged passage. Also, using carb cleaner and compressed air to thoroughly clean out the EGR passage are instrumental to success. If you are thorough, and meticulous, it can be done successfully without replacing the plenum.